This invention relates to a hydrophobic coating including diamond-like carbon (DLC) provided on (directly or indirectly) a substrate of glass, plastic, or the like, and a method of making the same. The coating may be deposited on the substrate utilizing plasma ion beam deposition in certain embodiments.
Conventional soda inclusive glasses are susceptible to environmental corrosion which occurs when sodium (Na) diffuses from or leaves the glass interior, as well as to retaining water on their surfaces in many different environments, including when used as automotive windows (e.g. backlites, side windows, and/or windshields). When water is retained or collects on automotive windows, the water may freeze (i.e. forming ice) in certain environments. Additionally, the more water retained on a windshield, the higher power wiper motor(s) and/or wiper blade(s) required.
In view of the above, it is apparent that there exists a need in the art for (i) a coated article (e.g. coated glass or plastic substrate) that can repel water and/or dirt, and a method of making the same, (ii) a coated soda inclusive glass where the coating(s) reduces the likelihood of visible stains/corrosion forming; and/or (iii) a protective hydrophobic coating for window, glass, or plastic substrates that is somewhat resistant to scratching, damage, or the like.
It is known to provide diamond like carbon (DLC) coatings on glass. U.S. Pat. No. 5,637,353, for example, states that DLC may be applied on glass. Unfortunately, the DLC of the ""353 patent would not be an efficient hydrophobic coating and/or would not be an efficient corrosion minimizer on glass in many instances.
U.S. Pat. No. 5,900,342 to Visser et al. discloses a fluorinated DLC layer on an electrophotographic element. From about 25-65% fluorine content by atomic percentage is provided at an outermost surface, to provide for low surface energy in an attempt to make removal of xerographic toner easier. Unfortunately, this DLC inclusive layer of the ""342 patent would be too soft for use on a glass substrate in automotive applications and the like. Its apparent lack of sp3 Cxe2x80x94C bonds and/or lack of Si-O bonds contribute to its softness. It is also believed that continuous exposure to sun, rain, humidity, dust, windshield wipers, and/or the environment in general would cause the ""342 DLC layer to break down or degrade rather quickly over time.
Thus, there also exists a need in the art for a DLC inclusive layer that has sufficient hardness and durability to withstand the environment while still exhibiting satisfactory hydrophobic qualities.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a durable coated article that can shed or repel water (e.g. automotive windshield, automotive backlite, automotive side window, architectural window, etc.).
Another object of this invention is to provide a coated substrate, wherein a coating includes sp3 carbon-carbon bonds and has a wettability W with regard to water of less than or equal to about 23 mN/m, more preferably less than or equal to about 21 mN/m, and most preferably less than or equal to about 20 mN/m, and in most preferred embodiments less than or equal to about 19 mN/meter. This can also be explained or measured in Joules per unit area (mJ/m2)
Another object of this invention is to provide a coated substrate, wherein a coating includes sp3 carbon-carbon bonds and has a surface energy xcex3C of less than or equal to about 20.2 mN/m, more preferably less than or equal to about 19.5 mN/m, and most preferably less than or equal to about 18 mN/m.
Another object of this invention is to provide a coated substrate, wherein a DLC inclusive coating has an initial (i.e. prior to being exposed to environmental tests, rubbing tests, acid tests, UV tests, or the like) water contact angle xcex8 of at least about 100 degrees, more preferably of at least about 110 degrees, even more preferably of at least about 115 degrees, and most preferably of at least about 125 degrees.
Another object of this invention is to provide a coating for a substrate, wherein at least about 15% (more preferably at least about 25%, and most preferably at least about 30%) of the bonds in the coating are sp3 carbon-carbon is (Cxe2x80x94C) bonds; and wherein the coating includes by atomic percentage at least about 5% silicon (Si) atoms (more preferably at least about 15%, and most preferably at least about 20% Si), at least about 5% oxygen (O) atoms (more preferably at least about 15% and most preferably at least about 20%), at least about 5% hydrogen (H) atoms (more preferably at least about 10% and most preferably at least about 15%) taking into consideration either the coating""s entire thickness or only a thin layer portion thereof. In certain embodiments, an increased percentage of H atoms may be provided near the coating""s outermost surface. In certain embodiments, the coating has approximately the same amount of C and Si atoms.
Another object of this invention is to provide a coating for a glass substrate, wherein the coating includes a greater number of sp3 carbon-carbon (Cxe2x80x94C) bonds than sp2 carbon-carbon (Cxe2x80x94C) bonds. In certain of these embodiments, the coating need not include any sp2 carbon-carbon (Cxe2x80x94C) bonds.
Another object of this invention is to provide a coated glass article wherein a DLC coating protects the glass from acids such as HF, nitric, and sodium hydroxide (the coating may be substantially chemically inert).
Another object of this invention is to provide a coated glass article that is abrasion resistant.
Another object of this invention is to provide a DLC coating on a substrate, wherein the coating includes different portions or layers with different densities and different sp3 carbon-carbon bond percentages. The ratio of sp3 to sp2 carbon-carbon bonds may be different in different layers or portions of the coating. Such a coating with varying compositions therein may be continuously formed by varying the ion energy used in the deposition process so that stresses in the coating are reduced in the interfacial portion/layer of the DLC coating immediately adjacent the underlying substrate. Thus, a DLC coating may have therein an interfacial layer with a given density and sp3 carbon-carbon bond percentage, and another layer portion proximate a mid-section of the coating having a higher density of sp3 carbon-carbon (Cxe2x80x94C) bonds. The outermost layer portion at the surface of the coating may be doped (e.g. addition of Si, O and/or F) so that this surface portion of the coating is less dense which increases contact angle and decreases the dispersive component of surface energy so as to improve hydrophobic characteristics of the coating.
Another object of this invention is to manufacture a coating having hydrophobic qualities wherein the temperature of an underlying glass substrate may be less than about 200xc2x0 C., preferably less than about 150xc2x0 C., most preferably less than about 80xc2x0 C., during the deposition of a DLC inclusive coating. This reduces graphitization during the deposition process, as well as reduces detempering and/or damage to low-E coatings already on the substrate in certain embodiments.
Generally speaking, this invention fulfills any or all of the above described needs or objects by providing a coated article comprising:
a substrate (e.g. glass or plastic);
a coating including diamond-like carbon (DLC) provided on said substrate, said coating including sp3 carbon-carbon bonds; and
wherein said coating has an initial contact angle xcex8 with a drop of water of at least about 100 degrees, and an average hardness of at least about 10 GPa.
This invention further fulfills any or all of the above described needs and/or objects by providing a coated glass article comprising:
a glass substrate; and
a coating including diamond-like carbon (DLC) provided on said glass substrate, wherein the outermost 5 xc3x85 of said coating includes in atomic percentage at least about 50% H.
This invention further fulfills any or all of the above described needs and/or objects by providing a coated glass article comprising:
a glass substrate comprising, on a weight basis:
SiO2 from about 60-80%,
Na2O from about 10-20%,
CaO from about 0-16%,
K2O from about 0-10%,
MgO from about 0-10%,
Al2O3 from about 0-5%;
a hydrophobic coating including diamond-like carbon (DLC) and sp3 carbon-carbon bonds provided on said glass substrate; and
wherein said hydrophobic coating has an initial contact angle xcex8 with a sessile drop of water of at least about 100 degrees, and an average hardness of at least about 10 GPa.
This invention further fulfills any or all of the above described needs and/or objects by providing a method of making a coated article, the method comprising the steps of:
providing a substrate; and
depositing a highly tetrahedral amorphous carbon (ta-C) inclusive coating having more sp3 carbon-carbon bonds than sp2 carbon-carbon bonds on the substrate in a manner such that the ta-C inclusive coating has an initial contact angle xcex8 of at least about 100 degrees.
In certain embodiments, the method includes plasma treating an outmost surface of the coating in order to provide at least H atoms in the coating proximate the outermost surface thereof so as to reduce surface energy of the coating.
This invention will now be described with respect to certain embodiments thereof, along with reference to the accompanying illustrations.